A patient's blood pressure is found to be very low following spinal anesthesia. This may be because the anest… - BSF Staff Nurse - 2015

BSF Staff Nurse - 2015

Medical & Surgical Nursing

Medium

Appeared in: BSF Staff Nurse - 2015

Explanation

Spinal anesthesia involves injecting a local anesthetic into the subarachnoid space, which blocks nerve roots.
This action includes blocking the sympathetic nerve fibers that are responsible for maintaining the tone of blood vessels.
The sympathetic blockade leads to widespread relaxation of vascular smooth muscle, causing both arterial and venous dilation (vasodilation).
This vasodilation decreases systemic vascular resistance and reduces venous return to the heart.
The combined effect is a drop in cardiac output and blood pressure, a common complication known as post-spinal hypotension.

Option A: This is the opposite of the actual effect. Spinal anesthesia causes vasodilation, not vasoconstriction.
Option C: This is incorrect. A sudden, sharp drop in blood pressure reduces blood flow to the kidneys, which would lead to a decrease, not an increase, in urine output. Furthermore, changes in urine output are a consequence, not the cause, of the hypotension.
Option D: While severe hypotension will eventually lead to decreased urine output due to poor kidney perfusion, this is a result of the low blood pressure, not the initial cause. The primary event causing hypotension is vasodilation.

Clinical Relevance

Nursing practice connection: Use the key finding related to Physiological effects of spinal anesthesia on the cardiovascular system to guide bedside assessment, documentation, and the next nursing action.
Hypotension is one of the most common and immediate complications of spinal anesthesia. Nurses must be prepared to recognize and manage it promptly to prevent adverse maternal and fetal outcomes.
Key nursing actions include pre-hydration with IV fluids, frequent monitoring of vital signs post-block, and readiness to administer vasopressors as per protocol.
Patient safety is paramount. The nurse should ensure emergency equipment and medications are readily available before the procedure begins.

How to Approach the Question

First, identify the key elements of the question: a patient with low blood pressure after receiving spinal anesthesia. The question asks for the cause.
Recall the basic mechanism of spinal anesthesia. It blocks nerve impulses, including sensory, motor, and autonomic (sympathetic) nerves.
Focus on the effect of blocking the sympathetic nervous system. The sympathetic system is responsible for the 'fight or flight' response, which includes maintaining blood vessel tone (vasoconstriction).
Deduce that blocking the sympathetic nerves will lead to a loss of this tone.
Connect the loss of vascular tone to its physiological effect: the blood vessels will relax and widen, which is called vasodilation.
Finally, relate vasodilation to blood pressure. Wider vessels mean less resistance and more space for blood to pool, leading to a drop in blood pressure. Select the option that matches this conclusion.

Concept Tested & Keywords

Concept Tested: Physiological effects of spinal anesthesia on the cardiovascular system.
Stem keywords: blood pressure, low, spinal anesthesia
Lead-in keywords: because

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